Zheng Mengli, Bai Yan, Sun Yingxia, An Jing, Chen Qinghua, Zhang Tieying
State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China.
Animals (Basel). 2023 May 25;13(11):1746. doi: 10.3390/ani13111746.
This study was conducted to investigate the effects of different proteases alone or in combination on protein digestibility of broilers. In vitro, the properties of four proteases in broilers, including acidic protease (AcP), alkaline protease (AlP), neutral protease (NeP) and keratinase (Ker), on endogenous protease activity and their effects on protein digestibility of common ingredients in broiler diets were investigated using a gut-mimicking model. In vivo, 640 1-day-old male broilers were randomly divided into 8 groups of 10 with 8 replicates of 10 birds per replicate cage. Eight dietary treatments included a corn-soybean meal basal diet (control), and the basal diet with 1.6 U AcP/g, 0.8 U NeP/g, 0.8 U AlP/g, 0.4 U Ker/g, 1.6 U AcP/g + 0.8 U NeP/g, 1.6 U AcP/g + 0.8 U AlP/g, or 1.6 U AcP/g + 0.4 U Ker/g added. The experiment lasted for 31 days. The results showed that the optimum pH values of AcP, NeP, AlP and Ker were 3.0, 9.0, 11.0 and 11.0 in vitro, respectively. Ker recovery proportion was 37.68% at pH 3.3-6.2. AcP alone or in combination with NeP, AlP or Ker increased in vitro crude protein digestibility (IVCPD) and decreased ileal apparent digestibility of crude protein in 31-day-old broilers ( < 0.05). All protease supplementation reduced the ileal apparent digestibility of amino acids compared to the control ( < 0.05). Acidic protease had a positive effect on trypsin and chymotrypsin activities, while AlP and Ker showed a negative effect. In vivo, average daily gain and average daily feed intake were significantly ( < 0.05) increased in broiler diets supplemented with AcP compared to the control group. When adding exogenous proteases to broiler diets, their sensitivity to digestive pH and their negative effects on endogenous protease activity, dosage and combination effects should be taken into account. In addition, the properties and dosage of proteases and the protein level in the feed should be considered.
本研究旨在探究不同蛋白酶单独或联合使用对肉鸡蛋白质消化率的影响。在体外，使用肠道模拟模型研究了肉鸡体内四种蛋白酶，包括酸性蛋白酶（AcP）、碱性蛋白酶（AlP）、中性蛋白酶（NeP）和角蛋白酶（Ker）对内源蛋白酶活性的影响及其对肉鸡日粮中常见成分蛋白质消化率的作用。在体内，将640只1日龄雄性肉鸡随机分为8组，每组10只，每个重复笼中有8个重复，每组10只鸡。八种日粮处理包括玉米 - 豆粕基础日粮（对照），以及添加了1.6 U/g AcP、0.8 U/g NeP、0.8 U/g AlP、0.4 U/g Ker、1.6 U/g AcP + 0.8 U/g NeP、1.6 U/g AcP + 0.8 U/g AlP或1.6 U/g AcP + 0.4 U/g Ker的基础日粮。试验持续31天。结果表明，体外实验中AcP、NeP、AlP和Ker的最适pH值分别为3.0、9.0、11.0和11.0。在pH 3.3 - 6.2条件下角蛋白酶回收率为37.68%。单独使用AcP或与NeP、AlP或Ker联合使用可提高31日龄肉鸡的体外粗蛋白消化率（IVCPD），并降低回肠粗蛋白表观消化率（P < 0.05）。与对照组相比，所有蛋白酶添加组均降低了回肠氨基酸表观消化率（P < 0.05）。酸性蛋白酶对胰蛋白酶和糜蛋白酶活性有积极作用，而AlP和Ker则表现出消极作用。在体内，与对照组相比，添加AcP的肉鸡日粮的平均日增重和平均日采食量显著增加（P < 0.05）。在肉鸡日粮中添加外源蛋白酶时，应考虑其对消化pH的敏感性、对内源蛋白酶活性的负面影响、剂量和组合效应。此外，还应考虑蛋白酶的性质和剂量以及饲料中的蛋白质水平。
